Acid-induced dimerization of imidates derived from glycine: Synthesis of methylN-(1,2,5-trisubstituted-4-imidazoyl)glycinates

A number of N-(1,2,5-trisubstituted-4-imidazoyl)-glycinates 4 were prepared in 60–95% yield from imidates 1 derived from α-amino esters by cyclodimerization without solvent at 70°C in acetic acid medium. According to this process, the reaction of imidate 1a as a 1,3-dipole generated in situ by thermal 1,2-prototropy with the free ethyl benzimidate as the dipolarophile has been investigated for the first time and gave directly the methyl imidazole-4-carboxylate in moderate yield by regioselective [3 + 2] cycloaddition. © 1996 John Wiley & Sons, Inc.